For certain construction projects, elongate members such as piles, anchor members, caissons, and mandrels for inserting wick drain material must be placed into the earth. It is well-known that such rigid members may often be driven into the earth without prior excavation. The term “piles” will be used herein to refer to the elongate rigid members typically driven into the earth.
One system for driving piles is conventionally referred to as a diesel ram for driving the pile and as a piston for compressing diesel fuel. Diesel fuel is injected into a combustion chamber below the ram member as the ram member drops. The dropping ram member engages an anvil member that transfers the load of the ram member to the pile to drive the pile. At the same time, the diesel fuel ignites, forcing the ram member and the anvil member in opposite directions. The anvil member further drives the pile, while the ram member begins a new combustion cycle.
An important factor in the operation of a diesel hammer is the quantity of diesel fuel injected into the combustion chamber because the ignition of the diesel fuel directly determines the driving forces applied to the pile. In particular, the quantity of diesel fuel determines both the forces on the anvil member both at the point of ignition and, because it affects how high the ram member goes, when the ram member impacts the anvil member on the compression stroke prior to ignition.
Conventional diesel hammers employ a variable fuel pump having a fuel chamber, a control pulley, and a control rope. The fuel chamber stores the fuel to be delivered to the combustion chamber. The angular orientation of the control pulley determines the effective volume of the fuel chamber. The control rope extends partly around the control pulley such that pulling on either end of the control rope causes the control pulley to rotate and change its angular orientation. Conventional variable fuel pumps require an operator to stand on the ground adjacent to the diesel hammer and pull the control rope to adjust the effective volume of the fuel chamber. The process of adjusting the amount of fuel delivered to the combustion chamber is thus cumbersome and conventional variable fuel pumps are typically placed in one setting and left there during the driving process.
The need thus exists for improved variable fuel pumps for diesel hammers.